Route guidance apparatus and method

ABSTRACT

A database stores map data including road network data and landmark data. A route search unit searches for a route from a departure point to a destination point from the road network data stored in the database. A road pattern analysis unit analyzes a route pattern of the route by referring to the road network data, and obtains road pattern data as the analysis result. A landmark selection area decision unit determines a landmark selection area for route guidance along the route based on the road network data and the road pattern data. A landmark selection unit selects landmark data included in the landmark selection area from said database. A route guidance information generation unit generates route guidance information of the route using the road pattern data and the landmark data selected by the landmark selection unit. A presentation unit presents the route guidance information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application PH2001-055847, filed on Feb. 28,2001; the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a route guidance apparatus and a methodfor executing route guidance for a pedestrian by presenting a routeguidance sentence or a simplified map.

BACKGROUND OF THE INVENTION

Recently, a route guidance apparatus for presenting a route guidancesentence and a simplified map to a destination for a pedestrian isdeveloped. This route guidance apparatus is a simple portable device oris loaded to a portable communication terminal such as a cellular-phoneor a personal data assistant (PDA).

A route guidance technique using the route guidance sentence and thesimplified map is disclosed in the following two references.

(1) TECHNICAL REPORT OF IEICE, PRU95-215(1996-02), “InteractiveGeneration of a Route and Its Application to Generating a Sketch MapDrawing in a Map Image Information System” Masahiko HORIE, ToshihiroKIMURA, Noboru BABAGUCHI, Seiichiro DAN and Tadahiro KITAHASHI

(2) TECHNICAL REPORT OF IEICE, PRMU96-156(1997-01), “Modeling ofGeographic Road Structure for Generation of Sketch Map Image andLinguistic Guide” Toshihiro KIMURA, Yoshihiro SUZUKI, Seiichiro DAN,Noboru BABAGUCHI and Tadahiro KITAHASHI

As for generation of the route guidance sentence, in reference (1), forexample, a sentence “Please go forward to the west direction by 20meters.” or “Please turn to the right at the junction.”, can bepresented. However, especially, numerical value representing distancesuch as “** meters” is difficult for a pedestrian to apply. Furthermore,innumerable junctions exist in a town area, and the pedestrian oftenmistakes a junction indicated by the route guidance sentence for anotherjunction. Accordingly, such route guidance sentence is not always easyfor the pedestrian to sufficiently understand.

In reference (2), for example, a route guidance sentence such as “Thisroad joins another road.” or “You advance to ** at a crossroads.”, isonly presented. This route guidance sentence is more difficult for thepedestrian to understand than the route guidance sentence disclosed inthe reference

Furthermore, in the reference (2), generation of a simplified map forguidance using a signpost for pedestrian (i.e., a landmark) isdisclosed. However, generation of a route guidance sentence using thelandmark is not disclosed in the references (1) or (2). In the reference(2), the target object is reserved. As for other landmarks, the landmarkfar from a main junction is removed in order to simply present thelandmark. However, if this method is used for generation of the routeguidance sentence, for example, a complicated route guidance sentenceusing many landmarks is generated at a place neighboring the mainjunction. Thus, easiness of the route guidance produces a contraryeffect.

As mentioned-above, in the known route guidance technique, presentationof the route guidance sentence is not always easy for the pedestrian tounderstand, and it often happens that the pedestrian misunderstands ajunction point, a joint point, or a divergence point indicated by theroute guidance sentence.

Furthermore, a method for effectively utilizing landmarks for generationof the route guidance sentence is not found. In short, it is impossibleto execute easy route guidance for the pedestrian by using landmarks.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a route guidanceapparatus and a method to present route guidance easy for the pedestrianto understand.

According to the present invention, there is provided a pedestrian routeguidance apparatus, comprising: a database configured to store map dataincluding road network data and landmark data; a route search unitconfigured to search for a route from a departure point to a destinationpoint from the road network data stored in said database; a road patternanalysis unit configured to analyze a route pattern of the route byreferring to the road network data, and to obtain road pattern data asthe analysis result; a landmark selection area decision unit configuredto determine a landmark selection area for route guidance along theroute based on the road network data and the road pattern data; alandmark selection unit configured to select landmark data included inthe landmark selection area from said database; a route guidanceinformation generation unit configured to generate route guidanceinformation of the route using the road pattern data and the landmarkdata selected by said landmark selection unit; and a presentation unitconfigured to present the route guidance information.

Further in accordance with the present invention, there is also provideda pedestrian route guidance method, comprising: storing map dataincluding road network data and landmark data in a database; searchingfor a route from a departure point to a destination point from the roadnetwork data stored in the database; analyzing a route pattern of theroute by referring to the road network data; obtaining road pattern dataas the analysis result; determining a landmark selection area for routeguidance along the route based on the road network data and the roadpattern data; selecting landmark data included in the landmark selectionarea from the database; generating route guidance information of theroute using the road pattern data and the selected landmark data; andpresenting the route guidance information.

Further in accordance with the present invention, there is also provideda computer program product, comprising: a computer readable program codeembodied in said product for causing a computer to execute pedestrianroute guidance, said computer readable program code having: a firstprogram code to store map data including road network data and landmarkdata in a database; a second program code to search for a route from adeparture point to a destination point from the road network data storedin the database; a third program code to analyze a route pattern of theroute by referring to the road network data; a fourth program code toobtain road pattern data as the analysis result; a fifth program code todetermine a landmark selection area for route guidance along the routebased on the road network data and the road pattern data; a sixthprogram code to select landmark data included in the landmark selectionarea from the database; a seventh program code to generate routeguidance information of the route using the road pattern data and theselected landmark data; and a eighth program code to present the routeguidance information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the route guidance apparatus according toone embodiment of the present invention.

FIG. 2 is a flow chart of route guidance processing according to oneembodiment of the present invention.

FIG. 3 is a schematic diagram of one example of a route to be searched.

FIGS. 4A and 4B are schematic diagrams of component example of node dataand arc data.

FIG. 5 is a schematic diagram of one example of divided route.

FIGS. 6A and 6B are schematic diagrams of road network data neighboringa junction point and analysis result of junction pattern.

FIG. 7 is a schematic diagram of various parameters representing ajunction pattern.

FIG. 8 is a schematic diagram of one example of a decision dictionary todecide a road pattern and an expression of route guidance.

FIGS. 9A and 9B are schematic diagrams of analysis example of thejunction pattern.

FIG. 10 is a schematic diagram of landmark selection area at a junction.

FIGS. 11A and 11B are schematic diagrams of a priority degree definitiontable for the landmark selection area.

FIG. 12 is a schematic diagram of a component example of landmark data.

FIGS. 13A and 13B are schematic diagrams of landmark selection on theway of the route.

FIGS. 14A and 14B are schematic diagrams of a comparison example of theroute guidance sentence according to the one embodiment and the priorart.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, various embodiments of the present invention will beexplained by referring to the drawings. FIG. 1 is a block diagram of apedestrian route guidance apparatus according to one embodiment of thepresent invention. The pedestrian guidance apparatus and method arepreferably optimized for the relative slow speed of a pedestrian, asopposed to a motor vehicle, as well as for the free movement of apedestrian unrestrained by motor vehicle restrictions such as turn lanesand one-way roads. Thus “pedestrian” is not strictly limited to a personwho travels by foot, but also applies to similar transportation modessuch as skate boards, scooters, wheelchairs, in-line skates, and evenbicycles.

In a database 1, basic data to generate a route guidance sentence and asimplified map along a route, such as map data, a route guidancesentence database used for generation of the route guidance sentence,and a simplified map database are stored. In the map data, in additionto map image, road network data and landmark data are included. In theroute guidance sentence database and the simplified map database, aplurality of presentation patterns corresponding to each road patternare included. Furthermore, in the simplified map database, thepresentation is stored as bit map data or vector data.

The database 1 may be set in the route guidance apparatus. However, iffunction of the route guidance apparatus is packaged in a portablecommunication terminal such as a cellular-phone, or if the routeguidance apparatus is composed as a dedicated portable device, thedatabase 1 is set outside the route guidance apparatus and connected tothe route guidance apparatus by wireless communication line.Furthermore, in the database 1 the map data and the landmark data may bean outside database set outside the route guidance apparatus, and theroute guidance sentence database and the simplified map database may bean inside database set in the route guidance apparatus.

A user input unit 2 is used for various kinds of input operation such askey operation or dial operation by a user using the route guidanceapparatus (i.e., a pedestrian). When the user inputs locationinformation of a departure place and a destination through the inputunit 2, road network data is read from the database 1 based on thelocation information, and supplied to a route search unit 3.

The route search unit 3 searches for a route from the departure place tothe destination using the location information input by the user inputunit 2 and the road network data read from the database 1, and generatesroute data represented by vector data.

A road pattern analysis unit 4 analyzes a road pattern of the route(pattern analysis) by referring to the road network data correspondingto the route data in the database 1. In this case, the road pattern is apattern of road included in the route and neighboring area of the route,which is explained in detail afterward. For example, the road patternincludes type (road attribute) representing whether the road is astraight route, whether the road is a junction point or a corner (crank,S curve), or whether the road is a station rotary. In addition to this,if the road is a junction point or a corner, the road pattern representsdetail pattern. An analysis method of the road pattern is explainedbelow.

The landmark selection area decision unit 5 determines a landmarkselection area necessary for route guidance along the route representedby the route data from the route search unit 3 and the road pattern datafrom the road pattern analysis unit 4.

The landmark selection unit 6 selectively reads out landmark datacorresponding to the landmark selection area selected by the landmarkselection area decision unit 5 from the database 1.

In a route guidance sentence generation unit 7 and a simplified mapgeneration unit 8, by using the route pattern data from the road patternanalysis unit 4, the landmark data selected by the landmark selectionunit 6 corresponding to the road pattern data from the database 1, andthe route guidance sentence database and the simplified map databasefrom the database 1, the route guidance sentence and the simplified mapare generated as route guidance information to guide a user along theroute data from the route search unit 3.

A presentation unit 9 is, for example, a display or a speaker. In thepresentation unit 9, based on the route guidance sentence data from theroute guidance sentence generation unit 7, a route guidance sentence ispresented by character sequence or speech. Furthermore, based on thesimplified map data from the simplified map generation unit 8, asimplified map along a route from the departure place to the destinationis displayed as an image. In this way, the route guidance sentence andthe simplified map are presented to the user.

In the above-mentioned component element in the route guidance apparatusin FIG. 1, a part of the database 1, the route search unit 3, the roadpattern analysis unit 4, the landmark selection area decision unit 5,the landmark selection unit 6, the route guidance sentence generationunit 7, and the simplified map generation unit 8 can be realized assoftware processing by a computer such as a route guidance apparatusterminal or a portable communication terminal.

Next, by following a flow chart shown in FIG. 2, the route guidanceprocessing of the present embodiment is explained. First, the user inputunit 2 is operated by a user who desires the route guidance, and adeparture point and a destination point are input (S101). As this inputoperation, in a condition that a map of place including a departureplace and a destination is displayed based on the map data from thedatabase 1 on a screen of the route guidance apparatus (a display of thepresentation unit 9), the user may indicate the departure point and thedestination point on the map by using a mouse, a cursor, a pen, or akey. Furthermore, the user may select the departure point and thedestination point from a list including landmarks, addresses and names.

Next, based on the departure point and the destination point input bythe user, and a route search condition, the route search unit 3 searchesa route from the departure point to the destination point (S102). As aroute search method, a route including a sidewalk may be preferablyselected. Furthermore, Dijkstra's method well known as an algorithm tofind the shortest route may be used. Of course, other methods of routesearch can be used. Briefly, it is sufficient that some route connectedfrom the departure place to the destination can be determined.Otherwise, the user may directly input the route on the map.

As a result of the route search, as shown in FIG. 3, route data from thedeparture point to the destination point represented by node and arc areobtained. For example, the node is represented as node data shown inFIG. 4A and the arc is represented as arc data shown in FIG. 4B. Thenode is a divergence point on the road network, for example, the nodeexists in a junction point and a corner. The arc is a line segmentconnecting two nodes. If a plurality of arcs is connected to one node,the plurality of arcs can be extracted by referring to connection fromthe node. Furthermore, by tracing from arc to node and from node to arcin order, a series of route lines can be traced.

Next, in the present embodiment, as shown in FIG. 5, the route searchunit 3 divides the route searched at S102 into at least three areas,i.e., a departure area, a destination area, and an intermediate area(route and junction area) (S103). Briefly, the route is divided intothree class parts and used for generation of the route guidance sentenceand presentation of the simplified map. By referring to FIG. 5, oneexample of route division processing is explained.

The departure area is an area from the departure place input by the userto the first target object. In FIG. 5, the departure place is a station.When the user walks from the station to the destination, a target objectfirst watched by the user is a post office. The departure area is thusthe area from the station to the post office. The departure area isimportant for a pedestrian to decide a direction to begin walking. Thedeparture area does not always include a road. Accordingly, specialexplanation is sometimes necessary for the route guidance sentence orthe simplified map.

The destination area is an area from the last target object to thedestination input by the user. In FIG. 5, the object last appearingalong the route is a school. The destination area is thus the area fromthe school to the destination. The road network is not always divided ata place of a pedestrian's target. Accordingly, special explanation issometimes necessary for the map, the route guidance sentence, or thesimplified map from the last target object to the destination.

In addition to the example post office and school, the target object maybe a signpost building such as a bank, a cinema theater, an eatinghouse, a supermarket and a convenience store, a signal, a junction name,a road name, road pattern such as a T-crossing or a junction, attendantobject to the road such as a pedestrian bridge and a marked crosswalk.In short, the target object is all object usable as the signpost for thepedestrian's walking. The route search unit 3 obtains information of thetarget object by referring to the road network data and the landmarkdata in the database 1. Furthermore, the route and junction area is aroad included in intermediate route except for the departure place andthe destination. The route and junction area includes a junction, acorner, and so on. In the present embodiment, the road pattern analysisis mainly executed for the route and junction area.

Next, the road pattern analysis unit 4 analyzes a road pattern of theroute searched at S102 (S104). If route division processing of S103 isexecuted after route search of S102, as mentioned-above, the roadpattern of the route and junction area is analyzed at S104. The roadpattern is mainly a pattern of intersection. The road pattern analysisrepresents which forked road the junction is, which degree the angledifference between a direction of entering road and a direction ofescape road, whether the road crosses a wide road at the junction,whether the road crosses an overpass. In short, a usable road pattern tobe analyzed based on the road network data is analyzed.

Next, based on the route data obtained at S102˜S103 and the road patterndata obtained at S104, the landmark selection area decision unit 5determines the landmark selection area to select the landmark along aroute represented by the route data (S105)

Next, the landmark selection unit 6 selectively reads out the landmarkdata from the database 1 in correspondence with the landmark selectionarea selected at S105 by the landmark selection area decision unit 5(S106).

Next, by referring to the road pattern data obtained at S104, thelandmark data selected from the database 1 at S106, and the routeguidance sentence database stored in the database 1, the route guidancesentence generation unit 7 generates a route guidance sentence includingan explanation of the road pattern and landmark names to guide a useralong the route determined at S102 (S107).

Furthermore, by referring to the road pattern data obtained at S102, thelandmark data selected from the database 1 at S106, and the simplifiedmap database stored in the database 1, the simplified map generationunit 8 generates a simplified map (S108).

Then, the presentation unit 9 presents the route guidance sentencegenerated at S107 by display of character sequence or speech.Furthermore, the presentation unit 9 presents the simplified mapgenerated at S108 by image display (S109).

Hereinafter, processing of each step in FIG. 2 is explained in detail.First, as a concrete example of analysis processing at S104 by the roadpattern analysis unit 4, analysis processing of junction pattern isexplained. The road pattern analysis unit 4 extracts road network dataof the route searched by the route search unit 3 from the database 1.For example, as shown in FIG. 6A, the road pattern analysis unit 4 setsa mask having a size several times the road width of advance directionon road network area and having a center point at the junction, andextracts the road network data included in the mask from the database 1.Next, the road pattern analysis unit 4 analyzes the road network area inthe area extracted by the mask (road network extraction area). As shownin FIG. 6B, the road pattern analysis unit 4 measures the number n (InFIG. 6B, n=4) of route lines each extended from the junction to outsideof the road network extraction area, a direction of each route line(angle difference between entering direction and a direction of eachroute), and a width of each route. By this road pattern analysis, theobject junction is decided such as “three-forked road”, “T-crossing andthe end”, “Y-crossing and forked road”.

In case that the road pattern analysis unit 4 analyzes a junctionpattern, the road pattern analysis unit 4 analyzes the road network datain the road network extraction area, and generates the following sevenparameters of junction pattern as shown in FIG. 7.

(1) The number n of roads each connected from the junction

(2) Angle difference θ₀ between the entering direction and the advancedirection for the junction in the clockwise direction

(3) Angle difference θ₁, θ₂ between the entering direction and eachdirection of other roads except for the advance direction for thejunction in the clockwise direction

(4) Angle difference θ_(L) between the advance direction and a directionof another road connected from the junction in the counterclockwisedirection

(5) Angle difference θ_(R) between the advance direction and a directionof the other road connected from the junction in the clockwise direction

(6) A ratio of road width “P=Wo/Wi” for the road width Wi of enteringdirection and the road width Wo of advance direction

(7) A ratio of road width “Q=max(W1, W2, . . . )/max(Wi, Wo)” for otherroad width W1, W2, . . . .

In FIG. 7, the angle difference θ₁, θ₂ of above (3) is not shown.

For example, in case of the junction pattern shown in FIG. 6B, thefollowing parameters except for θ₁, θ₂ are obtained.C(n, θ _(O), θ_(L), θ_(R) , P, Q)={4, 75, 105, 65, 100, 140}

Next, the road pattern analysis unit 4 compares the above-mentionedparameters with a decision dictionary shown in FIG. 8 in order to decidethe road pattern. In the decision dictionary shown in FIG. 8, the numberof roads (Hereinafter, it is called connection road) connected to anotice point such as the junction or the corner (In case of thejunction, the number is above-mentioned “n”), relation of angledifference between each connection road, road pattern including thejunction pattern based on the pedestrian's advance direction, andexpression of route guidance representing for the pedestrian how toadvance along the road are correspondingly stored. In FIG. 8, “Angle ofeach road (Angle difference for entering direction)” is angle differencebetween the entering direction and a direction of each road except forthe entering direction, and represented as “θ₀, θ₁, θ₂”. For example, ifthe number of connection roads is two (a road of entering direction anda road of advancing direction) , the road pattern is a straight road ora corner. The expression of route guidance is one of “Follow a road”,“Right-turn” and “Left-turn” based on angle of the advance direction. Onthe other hand, if the number of connection roads is three, the roadpattern is the junction of forked road. If the number of connectionroads is four, the road pattern is the junction of three-forked road.The forked road includes various cases, i.e., a case that each roaddiverges from the junction point at an interval of almost equal angle, acase that each road diverges at T-crossing (or the end), a case thateach road diverges at Y-crossing, and a case that the advance directionis straight but a branch road exists on the way. The case to which theforked Road is decided by combination of the angle difference betweenthe entering direction and each direction of other two connection roads.The expression of route guidance corresponding to the decided case isobtained. As for the three-forked road, based on combination of theangle difference between the entering direction and each direction ofother three connection roads, the expression of route guidance isdecided as one of “Go straight, and cross the road”, “Turn to the rightat the junction”, “Turn to the left at the junction”.

A threshold to decide the angle of each connection route is not limitedto values shown in FIG. 8. The threshold may be experimentallydetermined by making inquiries. In short, some decision standard isdetermined and stored as a database. The road pattern may be analyzedbased on this decision standard.

Furthermore, the decision of junction pattern can be executed by angleθ_(L), θ_(R), shown in FIG. 7. Concretely, suitable threshold is set tothe angle θ_(L) and θ_(R), such as a limit “10°˜80°” or a limit“80°˜100°”. For example, as shown in FIG. 9A, the junction pattern isdecided as Y-crossing because of “n=3, θ_(L)=θ_(R)=45°”. In the sameway, as shown in FIG. 9B, the junction pattern is decided as T-crossingbecause of “n=3, θ_(L)=θ_(R)=90°”. As for the junction, the road patternanalysis unit 4 outputs the above-mentioned junction pattern parameterand analysis result of the junction pattern as the road pattern data.

Next, referring to FIG. 10, the decision processing of landmarkselection area at S105 by the landmark selection area decision unit 5will be explained. The landmark selection area decision unit 5determines a landmark selection area based on geometrical informationincluding the route data from the route search unit 3 and the routepattern data from the road pattern analysis unit 4. FIG. 10 shows adecision example of the landmark selection area at the junction. Asmentioned-above, the junction pattern is analyzed by the road patternanalysis unit 4 as the following junction pattern parameters.C(n, θ ₀, θ_(L), θ_(R) , P, Q)={4, 75, 105, 65, 100, 140}

These parameters are called the geometrical information.

Next, a circle area of a radius “r” in which a junction point is thecenter is determined. The radius r is calculated by the followingfunction including road widths W1, W2, W3, W4 of the roads forming thejunction.r=L(W 1, W 2, W 3, W 4)

Next, by using the analysis result of the junction pattern, the circlearea is divided into four areas (selection areas 1, 2, 3 and 4 in FIG.10), i.e., area cut by each road line connected to the junction point.To each selection area 1, 2, 3 and 4, a priority degree corresponding tothe junction pattern parameter obtained by the road pattern analysisunit 4 is assigned. The priority degree is obtained by preparing a table(priority degree definition table) describing the priority degree ofeach area corresponding to the junction pattern parameter in thedatabase 1. In this way, in the landmark selection area decision unit 5,the landmark selection area is determined based on geometricalinformation of the route data and the road pattern data.

FIGS. 11A and 11B show examples of a priority degree definition table ofthe landmark selection area. FIG. 11A shows an example pattern in whichan advance road turns to the right direction, and FIG. 11B shows anexample pattern in which an advance road turns to the right at athree-forked intersection (crossroads). The higher the priority degreeis, the smaller the numerical value is. In FIG. 11A, the priority degreeof the right side area for the advance direction is high. In FIG. 11B,the priority degree of the lower right side area is the highest, thepriority degree of the upper left side area is the lowest, and thepriority degree of the lower left side area is the same as the prioritydegree of the upper right side area.

Next, landmark selection processing at S106 by the landmark selectionunit 6 is explained. In the landmark selection unit 6, by using thelandmark selection area determined by the landmark selection areadecision unit 5, landmark data representing landmarks included in thelandmark selection area are selectively obtained from the database 1.

In the database 1 in FIG. 1, the landmark data including items shown inFIG. 12 are stored for each landmark. In FIG. 12, “ID”is a numericalvalue representing identifier of the landmark. “Name” is a name of thelandmark such as a shop name or an institution name. “Class” representsa type of the landmark such as a gas station or a bank. “Prioritydegree” is a numerical evaluation standard to decide whether thelandmark is preferably used in case of route search or generation of aroute guidance sentence. “Position” is an X, Y coordinate of thelandmark (For example, the latitude and the longitude).

As for the landmark along the route, as shown in FIG. 13A, a landmark ofwhich a distance d1 is smaller is preferably selected from each landmarkin the landmark selection area. The distance d1 is calculated by thefollowing function F1 including the priority degree (α) of the selectionarea, a perpendicular distance (L) from the route, and the prioritydegree (β) of the landmark.d 1=F 1(L, α, β)

-   -   L: perpendicular distance from the route    -   α: priority degree of the selection area    -   β: priority degree of the landmark

As for the landmark of junction part, as shown in FIG. 13B, a landmarkhaving a shorter distance d2 is preferably selected from each landmarkin the landmark selection area. The distance d2 is calculated by thefollowing function F2 including the priority degree (α) of the selectionarea, a distance (L1) from the junction point, a perpendicular distance(L2) from entering route to the junction point, a perpendicular distance(L3) from escape route from the junction point, and the priority degree(β) of the landmark.d 2=F 2(L 1, L 2, L 3, α, β)

-   -   L1: distance from the junction point    -   L2: perpendicular distance from the entering route    -   L3: perpendicular distance from the escape route    -   α: priority degree of the selection area    -   β: priority degree of the landmark

Examples of the functions F1 and F2 are represented as follows.d 1=F 1(L, α, β)=α*β*L $\begin{matrix}{{d2} = {{F2}\quad\left( {{L1},{L2},{L3},\alpha,\beta} \right)}} \\{= {\alpha*\beta*\left( {{A*{L1}} + {B*{L2}} + {C*{L3}}} \right)\quad\left( {A,B,{C:\quad{constant}}} \right)}}\end{matrix}$

Next, generation processing of the route guidance sentence at S107 bythe route guidance sentence generation unit 7 is explained. In the routeguidance sentence generation unit 7, each unit guidance sentence isgenerated using the route data obtained by the route search unit 3, theroad pattern data obtained by the road pattern analysis unit 4, and thelandmark data selected by the landmark selection unit 6. The unitguidance sentence is a minimum sentence for executing route guidance tothe pedestrian. For example, (1) a sentence to guide from the departureplace to the first target object, (2) a sentence to guide from a targetobject to the next target object, (3) a sentence to guide from a cornerto the next target object, (4) a sentence to guide from the last targetobject to the destination, are regarded as the unit guidance sentence.The unit guidance sentence can be generated using a distance between twonodes, the landmark neighboring the node, the junction pattern, and thecorner state. Especially, if the target object is the junction, the roadpattern analysis unit 4 decides whether the junction pattern is a forkedroad (T-type, Y-type) or a three-forked road, and how to advance thethree-forked road by referring to the decision dictionary shown in FIG.8. Accordingly, an easy sentence using the junction pattern isgenerated.

In order to generate the unit guidance sentence, an expression modelcorresponding to the road pattern data generated by the road patternanalysis unit 4 is selected from the database 1. For example, assumethat the analyzed road pattern is the junction pattern represented bythe following parameter shown in FIG. 7.C(n, θ ₀, θ_(L), θ_(R) , P, Q)={4, 75, 105, 65, 100, 140}

In the database 1, following four expression models corresponding toabove parameters are registered.

-   -   {circle over (1)}TURN TO <TURN> AT <CROSS>.    -   {circle over (2)}TURN TO <TURN> AT THE CORNER OF <MARK>.    -   {circle over (3)}TURN TO <TURN> AT THIS SIDE OF <MARK>.    -   {circle over (4)}TURN TO <TURN> AT A CROSSROADS DISTANT BY        <DIST> METER FROM <MARK>.

In the above expression models, a junction name is assigned to <CROSS>,a landmark name is assigned to <MARK>, turn direction (the left or theright) is assigned to <TURN>, and a distance to the junction is assignedto <DIST>.

In this case, the expression model represents the expression of routeguidance corresponding to each road pattern in the decision dictionaryshown in FIG. 8.

Next, the landmark name of landmark selected by the landmark selectionunit 6, the junction name, and the distance from the junction areassigned to each unit guidance sentence. Each unit guidance sentencegenerated is combined along the route obtained by the route search unit3. As a result, route guidance which represents the route from thedeparture place to the destination as a series of sentences isgenerated.

FIGS. 14A and 14B show comparison examples of the route guidancesentence according to the present embodiment and the prior art. In FIG.14A, a part of underlines is special guidance sentence of the presentembodiment, which is not included in FIG. 14B of the prior art. Inshort, in the route guidance sentence of FIG. 14B, the third sentenceand the fourth sentence are difficult for a user to understand. However,in the route guidance sentences of FIG. 14A, the expression “A junction”is changed as “T-crossing” and “Y-crossing” as declared expression ofthe junction pattern, and the expression is intuitively easy for theuser to understand. Furthermore, in the route guidance sentences of FIG.14B, expressions such as “Turn to the right, go forward by 10 meters,and go forward to the left by 30 meters” are used. However, in the routeguidance sentence of FIG. 14A, this expression is changed to “Go forwardalong a crank by following the road.” as an easy sentence in which theroad pattern is briefly represented.

Furthermore, the ratio “P, Q” of road width in the road patternparameter shown in FIG. 7 may be used for generation of the routeguidance sentence by the route guidance sentence generation unit 7. Forexample, by using information of the ratio of road width, the unitguidance sentence such as “Go forward to a narrow road of the right sideby 50 meters at Y-crossing.” and “Go straight by 20 meters and turn tothe right on a wide road at the end of T-crossing.” can be generated.This unit route guidance sentence is easy for the pedestrian tounderstand.

As mentioned-above, in the present embodiment, the road pattern ismacroscopically analyzed. As for the junction, information for aplurality of roads connected to the junction point is generated as theroad pattern data. The area facing a plurality of roads connected to thejunction is determined as the landmark selection area based on the roadpattern data. The route guidance sentence is generated using thelandmarks selected from the landmark selection area. Accordingly, easyroute guidance sentences in which the landmark names are suitably usedcan be presented to the user.

Especially, in the present embodiment, the priority degree isrespectively assigned to each landmark included in map data of thedatabase 1. In the landmark selection area decision unit 5, as shown inFIG. 10, the priority degree is respectively assigned to a plurality oflandmark selection areas. In the landmark selection unit 6, as shown inFIGS. 13A and 13B, based on the priority degree of the landmarkselection area, the priority degree of the landmark included in the mapdata, and a distance from a route searched by the route search unit 3 tothe landmark, the landmark included in the landmark selection area issuitably selected. Accordingly, an easy landmark can be selectivelypresented to the user.

In the landmark selection area decision unit 5, as shown in FIGS. 10,11A, and 11B, at a part where the advance direction represented by theroute data turns, the priority degree of the landmark selection areainside the turn toward the advance direction is set higher than thepriority degree of other landmark selection areas. Accordingly, thelandmark attracting the user's attention during walking is preferablyused for the route guidance sentence.

Next, the generation processing of the simplified map at step S108 bythe simplified map generation unit 8 is explained. In the database 1, aplurality of presentation patterns corresponding to various road patterndata obtained by the road pattern analysis unit 4 are previously storedin order to generate the simplified map. The presentation patterns areregistered as bit map data or vector data in the simplified map databaseof the database 1, and used for representation of the simplified map. Incase of generating the simplified map, first, the presentation patterncorresponding to the road pattern data generated by the road patternanalysis unit 4 is selected from the database 1. For example, if theanalyzed road pattern is represented by the following parameters, aplurality of presentation patterns corresponding to the parameter isselected.C(n, θ _(O), θ_(L), θ_(R) , P, Q)={4, 75, 105, 65, 100, 140}

After the plurality of presentation patterns is selected based on theroute pattern (each junction, corner, and so on), they are connectedalong the guidance route. As a result, a simplified map from thedeparture point to the destination point along the guidance route isgenerated.

As mentioned-above, in the present invention, the road pattern such asthe junction on the route from the departure point to the destinationpoint is macroscopically analyzed, and the analysis result is reflectedin selection of landmarks included in the route guidance information.The route guidance information such as a route guidance sentence isgenerated using the analysis result and the landmark. As a result,useless or diffuse expression in the route guidance information can beremoved. Accordingly, the route guidance information is easy tointuitively understand.

A memory can be used to store instructions for performing the processdescribed above. Such a memory can be a CD-ROM, floppy disk, hard disk,magnetic tape, semiconductor memory, and so on.

Other embodiment of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with the true scope and spiritof the invention being indicated by the following claims.

1-22. (Cancelled)
 23. An apparatus for generating route guidanceinformation based on route information supplied from outside,comprising: a storage unit configured to store road network dataincluding a plurality of nodes and a plurality of arcs each connectingtwo nodes, and a plurality of expressions of route guidance incorrespondence with a junction pattern and an advance direction of thejunction pattern; a road pattern analysis unit configured to analyze anangle difference between two roads each connected to a junction of theroute information and a pattern of the junction by referring to the roadnetwork data; a route guidance information generation unit configured togenerate the route guidance information based on the expression of routeguidance corresponding to a result of the analysis; and a presentationunit configured to present the route guidance information.
 24. Theapparatus according to claim 23, wherein node data of each node includesa node identifier, a node position, a node name, the number of arcsconnecting the node, and an arrangement of arc identifiers connectingthe node; and wherein arc data of each arc includes an arc identifier,positions of a starting point, and an end point of the art, an arc name,and an arc width.
 25. A method for generating route guidance informationbased on route information supplied from the outside, comprising:storing road network data including a plurality of nodes and a pluralityof arcs each connecting two nodes, and a plurality of expressions ofroute guidance in correspondence with a junction pattern and an advancedirection of the junction pattern; analyzing an angle difference betweentwo roads each connected to a junction of the route information and apattern of the junction by referring to the road network data;generating the route guidance information based on the expression ofroute guidance corresponding to the analysis result; and presenting theroute guidance information.
 26. The method according to claim 25,wherein node data of each node includes a node identifier, a nodeposition, a node name, the number of arcs connecting the node, and anarrangement of arc identifiers connecting the node, and wherein arc dataof each are includes an arc identifier, positions of a starting pointand an end point of the arc, an arc name, and an arc width.